1. Field of the Invention
This invention relates to bearing and seal means for a moveable shaft. More particularly, the invention relates to a self-lubricating, thermoplastic shaft bearing and seal of simple, one-piece, construction for supporting a shaft and forming a seal around the circumference thereof.
2. Description of Prior Art
A wide variety of seals and/or bearings suitable for use with shafts, both rotary and reciprocating types, are known. Such seals or bearings are utilized in diverse applications, in pumps, fans, compressors and agitators, carburetors and the like. Bearing sealing means for rotatable or moveable shafts, used in automobile carburetors, for example, are described in U.S. Pat. Nos. 4,053,013 and 3,991,155.
Carburetors prepare and supply a mixture of fuel vapor and air, in proper proportion for efficient combustion, to cylinders of an engine. One of the important controls on a carburetor is the throttle valve which controls the amount of air-fuel mixture that enters the intake manifold. This control is used to change the speed of a vehicle. The throttle valve typically is round disk mounted on a rotatable shaft, so that it can be tilted at various angles in the carburetor throttle valve body. It is coupled by suitable linkage to the accelerator pedal in a vehicle. Depressing the pedal opens the throttle valve, permitting an increased amount of air-fuel mixture to reach the manifold. The shaft is supported by bearings on opposite sides of the carburetor housing.
Among bearings in common use are those which consist of fibers that are initially woven, twisted or braided into strands or shredded and then pressed or formed into coils, spirals, rings or other appropriate shapes. Useful materials employed to make such bearings include asbestos fabric, braided and twisted asbestos fibers, rubber and duck flax fibers, jute fibers and metallic fibers.
Generally, such types of bearings require lubrication in order to facilitate assembly with appropriate shafts and to extend their useful life. In addition, they also normally require appropriate packing or sealing means, such as sealing rings, which may generally be made of the same materials and which also require lubrication. Lack of lubrication causes both the bearing and sealing means to become hard and to lose their resiliency which results in increased friction, a diminished useful life, and consequently, increased operating costs. Moreover, such bearings and the sealing means employed therewith are disadvantageous in that the sealing means not only require frequent lubrication but also because of the quantity of fluid flow necessary to lubricate sufficiently both the bearing per se, as well as the sealing means.
The use of air lubricated bearings comprised of polytetrafluoroethylene (PTFE) (U.S. Pat. No. 3,837,717 to Kipple et al.) and oil or grease lubricated bearings comprised of polyphenylene sulfide (PPS) (U.S. Pat. No. 4,015,949 to Baker) is known. Baker also suggests a so called dry bearing by including PTFE with the PPS. U.S. Pat. No. 4,263,695 describes the use of a water lubricated bearing comprised of PPS and glass. And U.S. Reissue Pat. No. 31,110 to Black describes a solid axle wheel support in which there is employed a generally tubular thermoplastic bearing sleeve provided on its opposite axial ends with radially extending flanges which perform a sealing function.